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FreeBSD-EN-15:01.vt                                             Errata Notice
                                                          The FreeBSD Project

Topic:          vt(4) crash with improper ioctl parameters

Category:       core
Module:         vt
Announced:      2015-02-25
Credits:        Francisco Falcon from Core Security Technologies
Affects:        FreeBSD 9.3 and FreeBSD 10.1
Corrected:      2015-02-02 18:48:49 UTC (stable/10, 10.1-STABLE)
                2015-02-25 05:56:16 UTC (releng/10.1, 10.1-RELEASE-p6)
                2015-02-02 18:48:49 UTC (stable/9, 9.3-STABLE)
                2015-02-25 05:56:54 UTC (releng/9.3, 9.3-RELEASE-p10)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.freebsd.org/>.

I.   Background

The vt(4) device provides multiple virtual terminals with an extensive
feature set.

II.  Problem Description

The vt(4) code uses a signed integer as index value and does not test for
negative values.

III. Impact

A local attacker could trigger a panic by tricking the kernel into
accessing undefined kernel memory.

IV.  Workaround

No workaround is available, but systems that do not use vt(4) are not
affected.

All affected FreeBSD releases does not ship with vt(4) enabled by
default, and user have to enable them explicitly.

V.   Solution

Perform one of the following:

1) Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date.

2) To update your present system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

3) To update your present system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-15:01/vt.patch
# fetch https://security.FreeBSD.org/patches/EN-15:01/vt.patch.asc
# gpg --verify vt.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/9/                                                         r278106
releng/9.3/                                                       r279265
stable/10/                                                        r278106
releng/10.1/                                                      r279264
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-0998>

<URL:http://www.coresecurity.com/advisories/freebsd-kernel-multiple-vulnerabilities>

The latest revision of this Errata Notice is available at
https://security.FreeBSD.org/advisories/FreeBSD-EN-15:01.vt.asc

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